Blowout preventers of the ram-type have been provided with resilient packers which after use are often replaced. Such replacement has generally required that the bonnets be disconnected from the body and the rams pulled out of the body guideways. Such replacement procedure has generally required the removal of a minimum of four bolts or fasteners for each bonnet and the reinstallation and proper tensioning of such fasteners to secure the bonnets to the body.
One effort made to improve the ease of changing packers is illustrated on page 1438 of the 1980-81 Composite Catalog of Oil Field Equipment and Services, published by World Oil. This illustrates the hydraulic control system of Type "U" Preventers of Cameron Iron Works, Inc. Such system provides a pair of piston and cylinder connections between each of the bonnets and the body which utilize hydraulic pressure to move the bonnets away from the body or toward the body on tubes secured to the body. Ram closing hydraulic pressure is used to open the bonnets and ram opening pressure is used to close the bonnets. Such bonnet movement is prevented by the installation of four bolts in each bonnet which secure the bonnet to the body. After each packing change in this type preventer, eight bolts must be tightened and properly tensioned solely by the mechanical rotation of the bolts.